In a power switchgear (a main circuit switchgear) provided between a generator and a main transformer in a power station or the like, the conduction part, which is the main body of the power switchgear, is insulated and supported by insulating supports in atmospheric air (see, for example, Patent Literature 1).
Because the insulating supports need to support the conduction part, which is heavy, the insulating supports are formed from an epoxy-based molded insulating material, which generally has mechanical strength. Because the effect of soiling is taken into account, each of the insulating supports is provided with pleated parts to ensure there is a certain creepage distance. These pleated parts are molded from epoxy resin and to be one with the core part.
Patent Literature 2 describes an insulator molding method and a molding apparatus in which a long core made of FRP (Fiber Reinforced Plastics) or epoxy resin is sequentially moved to continuously mold a rubber exterior covering, which has a shading part, around the long core. With the method and apparatus mentioned above, it is regarded that an insulator can be easily and accurately molded by using a short mold.